The evolution of mobile communications systems and broadband multi-service networks are generally expected to merge in third-generation mobile systems that will provide global multimedia access to the mobile user. The concept referred to in Europe as the Universal Mobile Telecommunication System (UMTS) and globally as International Mobile Telecommunications in the year 2000 (IMT-2000) includes high-level access to multimedia services and evolution from second-generation mobile systems as key components. Standardization of this new system is carried out mainly by the 3rd Generation Partnership Project (3GPP) and the International Telecommunication Union—Telecommunication Standardization Sector (ITU-T).
UMTS/IMT-2000 separates the access functionality from the core network functionality, providing a common core network to support various types of access networks. Access networks provide core-network-technology-independent access platforms for mobile and other terminals to all core networks and network services. In order to support the convergence of fixed and mobile telecommunications networks, a common core network for both fixed and mobile access is envisaged.
Bandwidth at the air interface in the mobile access networks, which can vary greatly during calls, remains a limiting factor in the volume of information that can be transmitted to and from the wireless mobile terminals